The efficiency and safety of low‐dose apatinib combined with oral vinorelbine in pretreated HER2‐negative metastatic breast cancer

Abstract Background Apatinib is an oral small‐molecule tyrosine kinase inhibitor that blocks vascular endothelial growth factor receptor‐2. Oral vinorelbine is a semisynthetic chemotherapeutic agent of vinorelbine alkaloids. Apatinib and oral vinorelbine have been proved to be effective in the treatment of metastatic breast cancer (mBC). At present, several small sample clinical trials have explored the efficacy of apatinib combined with oral vinorelbine in the treatment of mBC. Methods This retrospective study included 100 human epidermal growth factor receptor‐2 (HER2)‐negative mBC patients who received low‐dose apatinib (250 mg orally per day) plus oral vinorelbine until disease progression or intolerance during February 2017 and March 2023. The progression‐free survival (PFS), overall survival (OS), objective response rate (ORR), clinical benefit rate (CBR), disease control rate (DCR), and safety were analyzed by SPSS 26.0 software and GraphPad Prism 8 software. Cox proportional hazards regression model for univariate and multivariate was used to identify factors significantly related to PFS and OS. Results The median follow‐up time for this study was 38.1 months. Among 100 patients with HER2‐negative mBC, 66 were hormone receptor (HR)‐positive/HER2‐negative and 34 were triple‐negative breast cancer (TNBC). The median PFS and OS were 6.0 months (95% CI, 5.2–6.8 months) and 23.0 months (95% CI, 19.9–26.1 months). There were no statistical differences in PFS (p = 0.239) and OS (p = 0.762) between the HR‐positive /HER2‐negative and TNBC subgroups. The ORR, CBR, and DCR were 21.0%, 58.0%, and 78.0%, respectively. Ninety‐five patients (95.0%) experienced varying grades of adverse events (AEs) and 38.0% of patients for Grades 3–4. The most common Grades 3–4 AEs that we observed were neutropenia (30.0%) and leukopenia (25.0%). Conclusion Low‐dose apatinib combined with oral vinorelbine demonstrates potential efficacy and well tolerated for pretreated HER2‐negative mBC.


| INTRODUCTION
Although the mortality of breast cancer is decreasing over the past years with the continuous development of treatment methods, metastatic breast cancer (mBC) is still incurable. 1The survival of human epidermal growth factor receptor-2 (HER2)-positive mBC has been significantly improved, which benefited by the development of anti HER2-targeted drugs (mainly including monoclonal antibodies, tyrosine kinase inhibitors [TKIs], and antibody drug conjugates [ADCs]). 2 HER2-negative breast cancer includes hormone receptor (HR)-positive/HER2-negative breast cancer, and triple-negative breast cancer (TNBC), accounting for 78%-85% of all breast cancer. 3,4Endocrine therapy is often used as the preferred treatment for HRpositive/HER2-negative mBC, but the treatment of endocrine resistant mBC patients generally needs to refer to the treatment of TNBC. 3 Chemotherapy is the main treatment for metastatic TNBC, but chemotherapy alone has a short remission time and is prone to drug resistance. 50][11] Compared to intravenous form, its oral form brings patients a higher quality of life and lower disease burden. 12Oral vinorelbine monotherapy or combined with other drugs have shown the efficacy for mBC. 13Previous studies reported that the objective response rate (ORR) of oral vinorelbine monotherapy in first-line setting of mBC was 29%-31% and the median progression-free survival (PFS) was 17.4 weeks to 5.2 months. 14,15However, when oral vinorelbine is used in combination with other drugs in first-line setting, the ORR reached 44.2%-51% and the PFS reached 8.4 months. 16,17Oral vinorelbine still shows certain therapeutic efficacy in second line treatment or subsequent treatment stages. 18,19umor angiogenesis plays a crucial role in the growth, invasion, and metastasis of malignant tumors. 20Based on this mechanism, antitumor angiogenesis therapy can be an effective means of treating malignant tumors. 21,22][29] Apatinib is a highly potent and selective oral small molecule TKI that blocks vascular endothelial growth factor receptor-2 (VEGFR-2). 30The clinical studies on mBC showed that apatinib monotherapy were effective with tolerable toxicity. 31,32The combination of apatinib and chemotherapy may enhance antitumor effect through their synergistic effects, 33 and some studies showed that apatinib combined with chemotherapy were effective for heavily pretreated mBC. 34,35The NAN trial included 66 patients with metastatic TNBC who were randomly treated with apatinib plus vinorelbine or vinorelbine at a ratio of 1:1.The result showed that the apatinib plus vinorelbine group has a significantly longer median PFS (3.9 vs. 2.0 months, p = 0.026). 36A Phase II study enrolled 40 patients with heavily pretreated HER2-negative mBC who were treated with apatinib plus oral vinorelbine, the median PFS was 5.2 months (95% confidence interval [CI], 3.4-7.0months). 37Another clinical trial of apatinib combined with oral vinorelbine in the treatment of metastatic TNBC is in progress, and the results have not yet been reported. 387][38] In our study, we analyzed the real-world data to investigate the efficacy and safety of low-dose apatinib (250 mg) combined with oral vinorelbine in pretreated HER2-negative mBC.The advantage of our study is that the low dose of apatinib may reduce the incidence of adverse events (AEs) associated with apatinib.And we attempt to identify patient characteristics that may benefit from this all-oral combination regimen.

| Study design
The present retrospective study collected the medical records of 100 patients with heavily pretreated HER2negative mBC at the National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College.These patients who received low-dose apatinib combined with oral vinorelbine during February 2017 and March 2023 were enrolled in our study.This study follows the Helsinki Declaration and has been approved by the National Cancer Hospital antiangiogenesis therapy, low-dose apatinib, metastatic breast cancer, oral vinorelbine & Shenzhen Hospital Ethics Committee (approval number: 2022-31-2).As this study is a retrospective study and patient anonymization, the Ethics Committee has determined to be exempt from signing informed consent forms.

| Patients and treatment
Eligible patients included: (1) female patients with age ≥18 years old; (2) histologically confirmed that the primary or metastatic tumor specimen was HER2-negative breast cancer (including HR-positive/HER2-negative breast cancer and TNBC); (3) HER2-negative status was defined as immunohistochemistry (IHC) 0-1+; or IHC 2+ and non-amplification by fluorescent in situ hybridization (FISH); (4) Eastern Cooperative Oncology Group (ECOG) performance status of 0-2; (5) distant metastatic lesions diagnosed through pathological or imaging examination.Patients are excluded if (1) they had diagnosis of the second primary malignant tumor in the past 5 years; (2) had positive or undefined HER2 status; and (3) the patient is currently participating in another clinical study.All patients enrolled in our study were treated with low-dose apatinib (250 mg orally per day, if patients presented with Grade 3/4 hematological AEs, hypertension, proteinuria, handfoot syndrome, or Grade 3/4 non hematological AEs that require medication intervention, delayed administration may be considered.Apatinib needs to be taken continuously until disease progression, or intolerance, or delayed for more than 21 days due to toxicity) and oral vinorelbine (take medication on the Days 1 and 8 of every 21 days, the first cycle dose for 60 mg/m 2 , and the subsequent cycles dose adjust to 80 mg/m 2 , if patients presented with Grade 3/4 hematological AEs or Grade 3/4 non hematological AEs that require medication intervention, dosage adjustment should be considered: oral vinorelbine should be reduced by 20% for the first dose and another 20% for the second dose.Oral vinorelbine needs to be taken continuously until the disease progresses or intolerance of toxicity even after dose adjustment).

| Data collection and assessment
We collect demographic and medical data of patients by querying the medical record system, including age, ECOG score, pathological features, site of metastasis, and previous treatment.Progression-free survival (PFS) was defined as the time from the beginning of oral administration of low-dose apatinib plus vinorelbine to tumor progression or death from any cause; overall survival (OS) was defined as the time from the start of apatinib based treatment to death from any cause; central nervous system (CNS) response refers to the evaluation of the response of brain lesions by researchers based on brain contrast-enhanced magnetic resonance imaging (MRI); overall response rate (ORR) was defined as the proportion of patients who got a complete response (CR) or partial response (PR); clinical benefit rate (CBR) was defined as the proportion of patients who got a CR or PR or stable disease (SD) for ≥24 weeks; disease control rate (DCR) was defined as the proportion of patients who got a CR or PR or SD.The efficacy was estimated by Response Evaluation Criteria In Solid Tumors (RECIST) version 1.1 (evaluated every two or three cycles during treatment), while toxicity was evaluated based on the 5.0 version of the Common Terminology Criteria for Adverse Events (CTCAE).

| Statistical analyses
All statistical analyses were performed utilizing SPSS 26.0 software (IBM Corp., Armonk, NY, USA) and GraphPad Prism 8 software (GraphPad Software, Inc., La Jolla, CA, USA).The survival data (PFS and OS) were estimated by the Kaplan-Meier method, and using the Cox proportional hazards regression model for univariate and multivariate analysis to identify factors significantly related to PFS and OS.All p-values and 95% CIs in this study were two-sided.A p-value < 0.05 was defined as statistically significant.

| Patient characteristics
The cutoff time for follow-up was October 31, 2023.Demographic and disease characteristics are shown in Table 1.The current study included 100 female patients with HER2-negative mBC.Among them, there were 66 patients of HR-positive/HER2-negative type and 34 patients of TNBC type.The median follow-up time for this retrospective study was 38.1 months (from 3 to 81.7 months).Seventy-eight patients (78.0%) had an Eastern Oncology Collaborative Group (ECOG) score of 0-1, while 22 patients (22.0%) had an ECOG score of 2. In addition, 32 patients (32.0%) had Grades 1-2 histological of tumors, and 68 patients (68.0%) were Grade 3. Forty-nine patients (49.0%) were diagnosed with Stage I-II at initial diagnosis, and 51 patients (51.0%) were diagnosed with Stage III-IV.Fifty-five of these patients (55.0%) experienced metastasis within 2 years or had distant metastasis at initial diagnosis, while 45 patients (45.0%) metastasized to distant lesions 2 years later.The median treatment line count for the HR-positive/HER2negative subgroup was four (range 2-11), while the the patients in our study have poorer clinical and pathological characteristics, and also indicates that their treatment will be more difficult.
As shown in Table 3, univariate analysis showed that patients initially diagnosed with Stage III-IV diseases (p = 0.002), DFS ≤24 months (p = 0.021), and received thirdline or above treatment (p = 0.003) may be more likely to progress from this combination therapy.Univariate analysis of OS showed that high-risk factors that may promote death include DFS ≤24 months (p = 0.031), received thirdline or above treatment (p = 0.008), with liver metastases (p = 0.033), and with brain metastases (p = 0.006).
In addition, we conducted a multivariate analysis of three factors that affect PFS in univariate analysis and found that patients initial diagnosed with Stage III-IV diseases (Stage I-II vs. III-IV, 8.0 vs. 4.5 months, HR = 0.592, p = 0.017) and received third-line or above treatment (Line 2 vs. ≥Line 3, 9.0 vs. 4.4 months, HR = 0.518, p = 0.005) would lead to a shorter PFS.A multivariate analysis was conducted on the four factors influencing OS in univariate analysis, and it was found that patients whose DFS ≤24 months (DFS ≤24 vs. >24 months, 17.0 vs. 24.0months, HR = 1.853, p = 0.019) and with brain metastases (without vs. with brain metastases, 24.0 vs. 13.0 months, HR = 0.485, p = 0.009) would lead to a shorter OS (seen in Table 4; Figure 3).
Our study included 25 patients with brain metastases from breast cancer (including 18 patients with HRpositive/HER2-negative and 7 patients with TNBC).The results showed that the PFS and OS of the total population F I G U R E 2 Survival curves in HER2-negative metastatic breast cancer patients treated with low-dose apatinib plus oral vinorelbine.(A) PFS curves of patients for HR-positive/HER2-negative and TNBC subgroups; (B) OS curves of patients for HR-positive/HER2-negative and TNBC subgroups.BC, breast cancer; HER2, human epidermal growth factor receptor-2; HR, hormone receptor; OS, overall survival; PFS, progression-free survival; TNBC, triple-negative breast cancer.
F I G U R E 1 PFS curve (A) and OS curve (B) of HER2-negative metastatic breast cancer patients treated with low-dose apatinib plus oral vinorelbine.CI, confidence interval; HER2, human epidermal growth factor receptor-2; OS, overall survival; PFS, progression-free survival.were 4.5 months and 13.0 months, the PFS and OS of the HR-positive/HER2-negative subgroup were 4.4 months and 12.0 months, and the PFS and OS of the TNBC subgroup were 4.5 months and 13.0 months, respectively.

| DISCUSSION
This retrospective study explored the efficacy and safety of low-dose apatinib combined with oral vinorelbine in the treatment of pretreated mBC.In this study, more than half of the patients (73 out of 100, 73.0%) had previously received at least two lines treatment in metastatic setting.The median PFS and OS of all 100 patients were   Although targeted therapy and biological immunotherapy have made great progress in recent years, chemotherapy is still one of the important treatment methods for mBC.Anthracyclines and/or taxanes are often used for (neo) adjuvant treatment in early stage or first-line treatment in metastatic setting, while there are no standards for selecting chemotherapy drugs for second-line treatment or above. 39ral vinorelbine exhibits antitumor activity not only in the first line but also in the patients previously treated with anthracyclines and taxanes. 13Previous studies have shown that the PFS of vinorelbine combined with capecitabine for second-line treatment of mBC was 3.4 to 3.8 months, and the OS was 11.3 months. 18,40From this, the efficacy of chemotherapy alone (such as oral vinorelbine combined with capecitabine) in second-line or above treatment does not seem satisfactory.In the second-line treatment of metastatic TNBC, sacituzumab govitecan (SG) significantly prolonged PFS (5.7 vs. 1.5 months, HR: 0.41) compared with chemotherapy of physician's choice (TPC). 41In heavily pretreated HR-positive/HER2-negative mBC patients, SG also significantly prolonged PFS compared with TPC (5.5 vs. 4.0 months, HR: 0.66). 42In patients with HER2-low advanced breast cancer, trastuzumab deruxtecan (T-Dxd) shows more encouraging efficacy (T-Dxd group vs. TPC group: 9.9 vs. 5.1 months, HR: 0.50). 8The emergence of these ADCs has brought new hope for HER2-negative mBC in later-line settings, however, few patients are able to receive these treatments due to their high prices.
Two clinical trials reported the PFS of apatinib monotherapy in the treatment of metastatic TNBC and non TNBC were 3.3 months and 4 months, respectively, with an ORR of 10.7% and 16.7%. 31,32A meta-analysis showed that the ORR of apatinib monotherapy for mBC was 20.4%, and the PFS was 4 months. 43Therefore, apatinib monotherapy has certain antitumor activity in mBC.When apatinib combined with chemotherapy, the efficacy seems to be better.The ORR of apatinib combined with chemotherapy for mBC was 22.7%-35.5%,5][46] A Phase II clinical trial about apatinib combined with oral vinorelbine for HER2-negative mBC demonstrated that the ORR was 17.1%, the PFS was 5.2 months and the OS was 17.4 months. 37Compared to these results, the PFS and OS in our study were both longer and had a higher ORR.As a second-line treatment, the median PFS of our study (9 months) also appears to be longer than the Phase II clinical study reported by Zhu et al. (6.1 months). 37The NAN trial results showed a median PFS of 3.9 months, an OS of 11.5 months, and an ORR of 9.1% for the treatment of metastatic TNBC treated with apatinib plus vinorelbine. 36In the TNBC subgroup in our study, the median PFS, OS, and ORR were 6.5 months, 22 months, and 23.5%, respectively, which seemed to be better than the results of the NAN study.
In addition, we analyzed the factors that affect PFS and OS, and found that patients who were initially diagnosed in Stages III-IV or received as a third-line treatment or beyond had a shorter PFS, while patients with DFS ≤24 months or with brain metastases had a shorter OS.Another real-world study of low-dose apatinib plus chemotherapy for mBC also showed that patients treated as third-line or above had worse PFS (treated as thirdline or above vs.first-or second-line: 3.5 vs. 5.1 months, p = 0.034). 44In the Phase II clinical study reported by Zhu et al., the PFS of patients treated ≥3 lines (5.2 months) was also shorter than that of patients treated <3 lines (6.1 months), but there was no statistically significant difference between the two group (p = 0.875). 37Our research findings indicated that patients with second-line treatment or initially diagnosed with Stages I-II have longer disease remission time, while patients who experience metastasis >24 months or without brain metastases have longer survival times.This discovery may help choose patients who would benefit from this all oral combination therapy.In terms of safety, the AE incidence rate calculated in this study was similar to previous reports, 37,47 and no new AEs were found.The majority of AEs were Grades 1-2, and the incidences of Grades 3-4 AEs were low, while most AEs can be relieved through dose reduction or symptomatic treatment.The any grade AEs with an incidence rate >40% in our study were myelosuppression, gastrointestinal reaction, secondary hypertension, hand-foot syndrome and proteinuria.The most common Grades 3-4 AEs that we observed were neutropenia and leukopenia.We found that compared to previous reports, the incidence of secondary hypertension (4%), hand-foot syndrome (2%) and proteinuria (2%) in Grades 3-4 in our study was lower, which were related to our use of lowdose apatinib.Based on these research results, it can be concluded that the antitumor activity of low-dose apatinib is not inferior to that of conventional dose, and its side effects and economic burden are lighter, making it a treatment option.
This is a retrospective study to evaluate the efficacy of low-dose apatinib combined with oral vinorelbine in the treatment of mBC.Due to limitations such as retrospective design, small sample size, lack of randomized controlled group, and confounding factors, bias may inevitably arise.As a result of these biases, the results of this study cannot be the basis for the treatment of all HER2-negative mBC.In the future, it needs to be confirm the efficacy of this alloral combination regimen through large-scale prospective randomized controlled clinical trials.However, these results show that low-dose apatinib combined with oral vinorelbine can effectively treat HER2-negative mBC with acceptable toxicity, which provides an alternative treatment for such patients.

| CONCLUSIONS
Finally, the findings of this retrospective study showed that low-dose apatinib combined with oral vinorelbine exhibits potential efficacy for pretreated HER2-negative mBC.Moreover, the regimen based on low-dose apatinib has mild adverse reactions and well tolerated.

F I G U R E 3
Survival curves in HER2-negative metastatic breast cancer patients treated with low-dose apatinib plus oral vinorelbine.(A) PFS curves of patients for initial diagnosed with Stage I-II and Stage III-IV subgroups; (B) PFS curves of patients treated for second line and third-line or above subgroups; (C) OS curves of patients whose DFS ≤24 and >24 months' subgroups; (D) OS curves of patients with and without brain metastases subgroups.DFS, disease-free survival; HER2, human epidermal growth factor receptor-2; OS, overall survival; PFS, progression-free survival.
Patient characteristics at baseline.
T A B L E 1 had previously received brain radiotherapy, and 2 patients (8.0%) had previously received brain surgery.In summary, more than half of patients in our study had received at least 2 lines treatment previously, or with visceral metastasis, or metastasis occurring within 2 years or had more than three metastatic sites.This indicates that Cox univariate regression analysis for progression-free survival and overall survival.Cox multivariate regression analysis for progression-free survival and overall survival.
Abbreviations: CI, confidence interval; DFS, disease-free survival; ECOG, Eastern Cooperative Oncology Group; HR, hazard ratio; TNM stage, the stage of tumor, node and metastasis Bold values represent p values < 0.05.T A B L E 3 Abbreviations: CI, confidence interval; DFS, disease-free survival; HR, hazard ratio; TNM stage, the stage of tumor, node and metastasis.Bold values represent p values < 0.05 T A B L E 4